Aerodynamic roll control system



Jan. 16, 1962 w. H. A. BOYD AERODYNAMIC ROLL CONTROL SYSTEM Filed July2, 1959 INVENTOR WILL/AM HUNTER A. BOYD United S ates. Patent O.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment to me ofany royalty thereon.

This invention relatesto an improved and simplified system forpreventing roll of a missile or bomb about its longitudinal axis whenthe missile is falling or flying in an air stream.

Known prior art roll control systems include systems with movablecontrol surfaces which operate to control or prevent roll byservomechanisms which are initiated by some type of sensing componentsuch as a gyroscope. Other systems use .a rotating gyro-wheel whichspins when the missile falls through an air stream and stabilizes amovable control surface to which the gyro-wheel is connected. Althoughthese known roll control systems usually operate satisfactorily, theyare too expensive and complex to use with small missiles or bombs.

It is an object of this invention, therefore, to provide an automaticroll control system which can be inexpensively and easily constructedfrom existing bomb and missile fins after a minor amount of modificationof the fin structure.

According to this invention, a conventional bomb or missile fin is cutto provide a fin section which remains fixed to the missile body, a flapand a trim tab. The flap and tab so out are hinged to the fin section atapproximately right angles to each other and are connected by a simplechannel-shaped linkage. The flap is very sensitive to missile roll andis connected to the tab in such a way that the tab will be moved uponmovement of the flap so as to produce a corrective aerodynamic forcewhich nullifies the roll of the missile.

The specific nature of the invention, as well as other objects, uses andadvantages thereof, will clearly appear from the following descriptionand from the accompanying drawing, in which:

FIG. 1 is a side elevation of a typical bomb or missile fin assemblywhich has been modified in accordance with this invention.

FIG. 2 is an end elevation of FIG. 1, showing a position which the flapand tab may assume as a result of missile roll.

FIG. 3 is an enlarged view of a channel member which connects the flapto the tab.

As shown in FIG. 1, the missile or bomb 10 has a conventional flat,triangular fin 11 affixed thereto at the tail end. The missile or bomb10 to which the fin is afi-lxed is of the conventional type having anelongated body with its longitudinal or roll axis X-X in the line offlight of the missile or bomb. Although only one fin is shown it is tobe understood that any desired number of fins may be modified so as toprovide hereinafter disclosed automatic roll control system. Fin 11 iscut along a line parallel to the roll axis to provide a flat stationarysection 12 and a flat triangular flap 13. Hinges 14 mount flap 13 to theoutermost edge 12a of section 12 for pivotal movement about an axiswhich is parallel to the longitudinal or roll axis of missile 10.

Affixed to the trailing edge 15 of section 12 is fiat, substantiallyrectangular trim tab 16 which is obtained by merely cutting asubstantially rectangular section from 3,016,827 Patented Jan. 16,- 1962ice fin 12. Tab 16 is pivotally mounted to the trailing edge 15 of fin12 by hinges 17. The axis about which trim tab 16 pivots issubstantially perpendicular to the roll axis of the missile 10.

Channel member 18 provides a relatively simple connection between flap13 and trim tab 16. This element, shown enlarged in FIG. 3, consists ofa substantially U-shaped channel section 19. Extending from channelsection 19 is a diverging shoulder section 20 and a converging section21. The ends 22 of section 21 are spacedapart a distance which isslightly wider than the distance between the sides forming U-shapedsection 19. Section 19 fits snugly over the surfaces of flap 13 and issecured to the trailing edge 15 of flap 13 by rivets or other suitableconnecting means.

Ends 22a and 22b have opposed edges 22a and 22b respectively, which arespaced apart a distance slightly greater than the thickness of tab 16.Because of the angle a between the shoulder section 20 and section 21,tab 16 will not be bent by edges 22a or 22b when flap 13 pivots onhinges 14. Angle a is approximately degrees.

As flap 13 pivots on hinges 14, one of the opposed edges 22a or 22b willcontact the opposite sides of tab 16 thereby pivoting that tab on hinges17. It will be evident that the particular edges 22a or 22b whichcontacts and drives tab 16 will depend upon the direction of pivoting offlap 13. Flap 13 pivotsin response to a greater air pressure against oneside than the other side of the flap.

For example, as shown in FIG. 2, if flap 13 is pivoted in a directionopposite that of arrow A, as a result of rotation of the missile 10about its roll axis in the direction of arrow A, edge 22b will be drivenagainst the surface of tab 16. The forceful engagement between edge 22band the surface of tab 16 will drive the free end of the tab towards thenose of missile 10 and de crease the angle between the tab and the flap13 from substantially degrees to some angle less than 180 degrees. Thedirection of pivot of tab 16 is indicated by arrow B in FIG. 2. Movementof tab 16 in the direction of arrow B will provide an inclined surfaceto the air stream. This inclined surface will produce a torque on finsection 12. which is opposite in direction to that shown by arrow A. Asa result, the missile 19 will be automatically stabilized against roll.Should missile 10 roll in a direction opposite in direction to thatshown by arrow A, flap 13 and tab 16 will move in an opposite directionto that shown in FIG. 2 and thereby automatically prevent roll in thisdirection.

Although fiap 13 is shown as triangular in shape, the

particular shape is not critical. The flap will function satisfactorilyeven though it is some other configuration, such as rectangular, as longas the flap is mounted for rotation about an axis which is substantiallyparallel to the roll axis of the bomb or missile 10.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction and arrangmentwithin the scope of the invention as defined in the appended claims.

I claim as my invention:

1. A roll control system for a missile having an elongated body with thelongitudinal axis in the line of flight of said missile, said systemcomprising: a fin section mounted on the tail end of said missileperpendicular to the longitudinal axis thereof, a flap pivotally mountedto the end of said fin section, said flap adapted to move in response toan increase in air pressure on one side thereof as a result of missileroll about an axis substantially parallel to said longitudinal axis, atrim tab pivotally mounted to the trailing edge of said fin for pivdtalmovement about an axis Substantially perpendicular to said longitudinalaxis,- and a channel member, one end of said member being fixed to thetrailing edge of said flap and the other end fprming a painqf spacedsa'rt 'dges'adapte d to alternately Contact opposite faces bf saidtfii'ntab depending upon the direetion of move mentor said flap g 7 V V 2. Aroll control system as defined in claim 1, wherein one end df 'said'Channel member cbmprises a pair of sp'aeed apart parallel edges adaptedto fit over a ortion 10 2,520,665

4 of the trailing edge of said flap, a pair of opposed edges on theother end of said member, said edges being spacedapart a distanceslightly greater than the width of said tab so that each edge canalternately contact one face 5 of said trim tab upon movement of saidfiap..

References Cited in the file of this patent UNITED STATES PATENTSWilliams Feb. '20, izs Warren Aug. 29, 1950 t I l l

